npomarede wrote:Nope, Hatari supports alt-ram for Falcon and TT mode since Hatari 1.9, which was quite a lot of changes to handle, as this requires 32 bit support in memory access thus a 68030 cpu, and not a 68000.
I wasn't precise enough. I should mentioned that I was referring to the ST series. I wasn't talking about the TT/Falcon, for them Hatari has dedicated TT-RAM size setup.
npomarede wrote:mfro is right, alt ram (also called fast ram on TT) starts at $100000, not at $40000 as you suggest.
This is why blitter/fdc/hdc can't transfer data directly to alt RAM, and that's also why the CT60 for example came with a patched tos that redirected lots of OS calls to works in 32 bit mode.
Again, I'm talking about the ST.
MMU chip in the ST series supports max 4MB of ST-RAM: range from $0 to $3FFFFF. Main impact of that limitation is that on the real hardware you are not able to:
- set Shifter video address beyond $400000 memory address;
- set DMA address beyond $400000 memory address;
- SoundDMA address beyond $400000 memory address.
Only BLiTTER have access to the full 24bit memory range.
On the ST when you need more ram than 4MB you should install ALT-RAM board and appropriate driver.
That driver should install "_FRB" cookie and add additional memory with Maddalt function.
After that, you can address ALT-RAM with Mxalloc function because on the ST Malloc is limited to $0 to $3FFFFF address range.
Usually ALT-RAM starts from address $400000.
And now back to emulators.
Currently, when you set the RAM to 14MB in Hatari/Steem then they behaves differently than the ST:
- you are able to set Shifter/DMA/SoundDMA to ANY memory area, also beyond $400000;
- you can address ANY memory are with Malloc, also beyond $400000;
- there is no "_FRB" cookie.